Without limiting the scope of the present invention, its background will be described with reference to treating multiple hydrocarbon bearing subterranean zones in a well, as an example.
It is common to encounter hydrocarbon wells that traverse more than one separate subterranean hydrocarbon bearing zone which may have similar or different characteristics. Production of hydrocarbons from these separate subterranean zones can be enhanced by performing various treatments. Examples of well treatments include fracturing, gravel packing, frac packing, chemical treatment and the like. The zone's particular characteristics determine the ideal treatments to be used. Accordingly, in multi zone wells, different well treatments may be required to properly treat the different zones.
For example, one or more of the zones may be an unconsolidated or poorly consolidated zone which may result in the production of sand along with the hydrocarbons if a sand control treatment is not performed. Specifically, it may be desirable to perform a gravel pack treatment in such an unconsolidated zone to control sand production from the well. The gravel pack treatment serves as a filter and helps to assure that fines and sand do not migrate with produced fluids into the wellbore.
In a typical gravel pack completion, a screen consisting of screen units is placed in the wellbore within the zone to be completed. The screen is typically connected to a tool having a packer and a crossover. The tool is in turn connected to a work or production string. A particulate material, usually graded sand (often referred to in the art as gravel) is pumped in a slurry down the work or production string and through the crossover whereby it flows into the annulus between the screen and the wellbore. Some of the liquid forming the slurry may leak off into the subterranean zone with the reminder passing through a screen sized to prevent the sand in the slurry from flowing therethrough. The transport fluid then returns to the annulus through the washpipe inside the screen that is connected to the workstring. As a result, the sand is deposited in the annulus around the screen whereby it forms a gravel pack. The size of the sand in the gravel pack is selected such that it prevents formation fines and sand from flowing into the wellbore with produced fluids.
As pointed out above, when a well intersects multiple spaced formation zones, each zone may require separate or even different successive treatments. In these multiple zone wells, a need arises to mechanically isolate the separate zones so that they may be individually treated. In the selected gravel packing treatment example, a multiple zone well may require that each zone be isolated and connected to the surface and treated individually. For example, undesirable fluid losses and control problems could prevent simultaneous gravel packing of multiple zones. In addition, each zone may require unique treatment procedures and subsequent individual zone testing and treatment may be required.
Conventional methods of isolating individual zones for treatment utilize multi-trip processes of setting temporary packers. To overcome these time consuming and expensive conventional methods, one-time hydraulic operated sleeves have been used to provide access to a zone after it has first been treated. When the zone is to be opened, the tools' hydraulically operated sleeve valve is opened as the well pressure is raised to a preset level and then bled off. These tools are one-shot in that they are installed in the closed position and once opened cannot be later closed to again isolate that particular zone. These prior systems and methods do not allow the zones to be selectively and repeatedly isolated for subsequent treatment and monitoring.
A need has therefore arisen for an apparatus that provides for the isolation of separate zones traversed by a wellbore such that individualized treatment processes may be performed on the separate zones. A need has also arisen for such an apparatus that can prevent fluid loss from one zone to the next during such individualized treatment processes. Further, a need has arisen for such an apparatus that can be reopened after the individualized treatment processes have been completed to allow for final completion and production from the multiple zones.